doc: Update documentation for DBConnection and session handling

Author: daireto

docs/api/db-connection-helper.md

@@ -41,8 +41,7 @@ The `DBConnection` class has the following methods:
 
 #### init_db
 
-Initialize the database tables. It also sets the session of the base model to
-the `async_scoped_session` async session factory:
+Initialize the database tables for the given base models:
 
 ```python
 from sqlactive import DBConnection
@@ -53,7 +52,7 @@ asyncio.run(conn.init_db()) # Initialize the database
 ```
 
 If your base model is not `ActiveRecordBaseModel` you must pass
-your base model class to this method in the `base_model` argument:
+your base model. You can also initialize multiple base models at once:
 
 ```python
 from sqlactive import DBConnection, ActiveRecordBaseModel
@@ -67,12 +66,13 @@ class BaseModel(ActiveRecordBaseModel):
 DATABASE_URL = 'sqlite+aiosqlite://'
 conn = DBConnection(DATABASE_URL, echo=True)
 asyncio.run(conn.init_db(BaseModel)) # Pass your base model
+# or
+asyncio.run(conn.init_db(BaseModel, AnotherBaseModel)) # Pass multiple base models
 ```
 
 #### close
 
-Close the database connection. It also sets the session of the base model
-to `None`:
+Close the database connection and remove the session:
 
 ```python
 from sqlactive import DBConnection
@@ -83,26 +83,5 @@ asyncio.run(conn.init_db())
 
 # Perform operations...
 
-asyncio.run(conn.close()) # Close the database connection
-```
-
-If your base model is not `ActiveRecordBaseModel` you should pass
-your base model cl0ass to this method in the `base_model` argument:
-
-```python
-from sqlactive import DBConnection, ActiveRecordBaseModel
-
-# Note that it does not matter if your base model
-# inherits from `ActiveRecordBaseModel`, you still
-# need to pass it to this method
-class BaseModel(ActiveRecordBaseModel):
-    __abstract__ = True
-
-DATABASE_URL = 'sqlite+aiosqlite://'
-conn = DBConnection(DATABASE_URL, echo=True)
-asyncio.run(conn.init_db())
-
-# Perform operations...
-
-asyncio.run(conn.close(BaseModel)) # Pass your base model
+asyncio.run(conn.close()) # Close the database connection and remove the sessions
 ```

docs/api/native-sqlalchemy-queries.md

@@ -1,49 +1,21 @@
 # Native SQLAlchemy queries
 
 You can asynchronously execute native SQLAlchemy queries using the
-`sqlactive.conn.execute` function. It uses the
-[`AsyncSession`](session-mixin.md) of the `ActiveRecordBaseModel` class and
-return a buffered `sqlalchemy.engine.Result` object.
+`sqlactive.conn.execute` function. It uses a `sqlalchemy.ext.asyncio.async_scoped_session`
+instance to perform the actual query.
 
 ## Usage
 
 ```python
 from sqlalchemy import select, func
-from sqlactive import execute
+from sqlactive import DBConnection, execute
+
+conn = DBConnection(DATABASE_URL, echo=True)
 
 query = select(User.age, func.count(User.id)).group_by(User.age)
-result = await execute(query)
+result = await execute(conn.async_scoped_session, query)
 ```
 
 The `statement`, `params` and `kwargs` arguments of this function are the
 same as the arguments of the `execute` method of the
 `sqlalchemy.ext.asyncio.AsyncSession` class.
-
-If your base model is not `ActiveRecordBaseModel` you must pass your base
-model class to the `base_model` argument of the `execute` method:
-
-```python
-from sqlalchemy import select, func
-from sqlactive import ActiveRecordBaseModel, execute
-
-# Note that it does not matter if your base model
-# inherits from `ActiveRecordBaseModel`, you still
-# need to pass it to this method
-class BaseModel(ActiveRecordBaseModel):
-    __abstract__ = True
-
-class User(BaseModel):
-    __tablename__ = 'users'
-    # ...
-
-query = select(User.age, func.count(User.id)).group_by(User.age)
-result = await execute(query, BaseModel)  # or execute(query, User)
-```
-
-???+ warning
-
-    Your base model must have a session in order to use this method.
-    Otherwise, it will raise an `NoSessionError` exception.
-    If you are not using the `DBConnection` class to initialize
-    your base model, you can call its `set_session` method
-    to set the session.

docs/api/session-mixin.md

@@ -67,12 +67,3 @@ def set_session(session: async_scoped_session[AsyncSession])
 > # Set the session
 > ActiveRecordBaseModel.set_session(async_scoped_session(AsyncSession))
 > ```
-
-#### close_session
-
-```python
-@classmethod
-def close_session()
-```
-
-> Close the async session.